Production of high-purity magnesium hydroxide (Mg(OH).sub.2) for uses such as flame retardants and pharmaceuticals by known processes involves numerous energy-intensive steps as well as high cost chemical usage. Various processes for such production are described in U.S. Pat. No. 5,476,642; No. 5,286,285; No. 5,143,965; No. 4,698,379; and No. 4,695,445.
In a flue gas desulfurization process, controlling alkalinity of process slurry prevents the formation of scale which is detrimental to the system. Magnesium-enhanced lime is used to increase alkalinity of the process slurry through the formation of magnesium sulfite (MgSO.sub.3). Lime presenting a magnesium oxide (MgO) content is selected for such use to enable the formation of the magnesium sulfite. Such process slurry is a lime slurry containing magnesium ions. A portion of such magnesium sulfite laden slurry is bled from the desulfurization system to maintain slurry chemistry. Its disposal can present high costs and environmental concerns.
Such bleed-off slurry provides an economical source of feedstock for the production of high purity magnesium hydroxide.